1. Field of the Invention
The present invention relates to a shaft assembly for use in a washing machine, and more particularly, to a shaft assembly which can prevent noise generated from a speed reduction gear assembly therein.
2. Prior Art
A general automatic washing machine has, as shown in FIG. 1, a washing tub 4 supported by a plurality of suspensions 15 in an outer casing 1, a dehydration tub 5 accommodated in the washing tub 4, a pulsator 6 installed at the bottom of the dehydration tub 5, a motor 7 for driving the pulsator 6, and a shaft assembly 8 for transmitting a driving force of the motor 7 to the pulsator 6 and the dehydration tub 5.
A top cover 2 covers the upper part of the outer casing 1, and a water supply device 3 for supplying the washing tub 4 and the dehydration tub 5 with washing water is installed at the upper part of the washing tub 4. At the lower side of the washing tub 4 is installed a drain device 9 for draining the water in the washing tub 4 and the dehydration tub 5 after a washing operation.
When the washing machine begins to operate, the washing water is supplied to the washing tub 4 and the dehydration tub 5 through the water supply device 3, and when the water supplying operation is completed, the motor 7 begins to operate. The torque of the motor 7 is transmitted to the shaft assembly 8 through a belt 7a, and then the shaft assembly 8 rotates the pulsator 6. The rotation of the pulsator 6 causes the vortex water flow in the dehydration tub 5, and laundry accommodated in the dehydration tub 5 is washed by the vortex water flow.
When the washing operation is completed, the washing water in the dehydration tub 5 is drained outside through drain ports 5a formed at the side of the dehydration tub 5 and the drain device 9. When the draining operation is completed, a dehydration operation begins.
In the dehydration operation, the motor 7 drives at a high speed, and the shaft assembly 8 transmits the torque of the motor 7 to the pulsator 6 and the dehydration tub 5 simultaneously. Then the dehydration tub 5 and the pulsator 6 are rotated altogether at a high speed, and thereby the laundry is dehydrated by a centrifugal force.
FIG. 2 is an enlarged side sectional view of the shaft assembly 8, and FIG. 3 is a partial enlarged view of FIG. 2. The shaft assembly 8 has an input shaft 24 and an output shaft 29 which are inserted respectively at a lower housing 21 and an upper housing 20, a speed reduction gear assembly 10 disposed between the input shaft 24 and the output shaft 29, a hollow shaft 23 installed outside the input shaft 24 to be coaxial with the input shaft 24, a dehydration shaft 30 installed outside the output shaft 29 to be coaxial with the output shaft 29, bearings 22a and 22b supporting the hollow shaft 23 and the dehydration shaft 30 to be capable of rotating, and a clutch lever 32 for selecting the washing operation and dehydration operation.
A shaft pulley 24a is installed at the input shaft 24, and the shaft pulley 24a is connected with the motor 7 through a belt 7a. The input shaft 24 and the hollow shaft 23 are connected with each other by a clutch spring 26. The clutching operation of the clutch spring 26 is controlled by a clutch sleeve 25 which is operated by the clutch lever 32.
The speed reduction gear assembly 10 is comprised of a break drum 28, an internal gear 27 being fixed at the break drum 28, a sun gear 24b being disposed coaxially with the internal gear 27 and being formed at the upper end part of the input shaft 24 in a body with the input shaft 24, and a plurality of planet gears 28a being installed around the sun gear 24b and being engaged with the internal gear 27 and the sun gear 24b. The shafts 28b of respective planet gears 28a are rotatably supported by an upper carrier 33 and a lower carrier 34, and the upper carrier 33 is fixedly connected to the output shaft 29 and rotates together with the output shaft 29. The output shaft 29 is connected to the pulsator 6.
While the break drum 28 is fixed by an external force, when the input shaft 24 rotates, the planet gears 28a are rotated by the sun gear 24b. The output shaft 29 is rotated by the rotation of the planet gears 28a. In this situation, since the planet gears 28a are rotated at a lower speed than the rotational speed of the sun gear 24b, the output shaft 29 is rotated at a lower speed than the rotational speed of the input shaft 24, and thereby the rotation of the input shaft 24 is transmitted to the output shaft 29 in a speed reducing manner. Therefore, the pulsator 6 rotates at a low speed when the motor 7 rotates.
The break drum 28 is connected with the hollow shaft 23 at the lower side thereof and with the dehydration shaft 30 at the upper side thereof. Therefore, the hollow shaft 23, the break drum 28 and the dehydration shaft 30 will rotate altogether. The dehydration shaft 30 is connected to the dehydration tub 5.
While the input shaft 24 and the hollow shaft 23 are fixed with each other along the rotational direction thereof by the clutch spring 26, if the shaft pulley 24a is rotated, the break drum 28 is rotated by the shaft pulley 24a, and the dehydration shaft 30 is rotated by the break drum 28. Thus, the dehydration tub 5 is rotated at a high speed, and the laundry accommodated in the dehydration tub 5 is dehydrated.
The clutch lever 32 is driven by a drain motor which is not shown in the figure. The clutch lever 32 controls a break band 31 disposed at a side of the break drum 28 and the clutch sleeve 25, simultaneously.
In the washing operation, the clutch lever 32 drives the break band 31 to break the break drum 28, and drives the clutch sleeve 25 to release the clutch spring 26. Accordingly, the torque of the shaft pulley 24a is transmitted to the pulsator 6 through the input shaft 24, the speed reduction gear assembly 10, and the output shaft 29, and then the pulsator 6 rotates at a low speed.
In the dehydration operation, the clutch lever 32 drives the break band 31 to release the break drum 28, and drives the clutch sleeve 25 to perform the clutching operation of the clutch spring 26. Then, the shaft pulley 24a rotates the input shaft 24 together with the hollow shaft 23, and then the break drum 28 and the dehydration shaft 30 are rotated together with the hollow shaft 23. Accordingly, the dehydration tub 5 connected with the dehydration shaft 30 is rotated at a high speed.
In such a shaft assembly 8 for use in a washing machine, there is a problem that noise is generated from the speed reduction gear assembly 10 during the washing and dehydrating operations. That is, since the speed reduction gear assembly 10 is comprised of a plurality of gears 24b, 27, and 28a, the noise is generated due the tolerance of the gears 24b, 27, and 28a when the input shaft 24 rotates.
In order to reduce such a noise, a shaft assembly has been proposed in which the gears 24b, 27, and 28a in the speed reduction gear assembly 10 are helical gears. However, since the sun gear 24b is formed in a body with the input shaft 24, it is so hard to form the sun gear 24b into a helical gear.
Furthermore, if the gears 24b, 27, and 28a are comprised of the helical gears, there is a problem that noise caused by a thrust between the gears 24b, 27, and 28a occurs when the input shaft 24 rotates. That is, when the input shaft 24 rotates, the sun gear 24b or the planet gears 28a are moved up and down by the thrust of the helical gears, so the sun gear 24 may strike against the output shaft 29, or the planet gears 28a may strike against the upper carrier 33 or lower carrier 34. Thus the speed reduction gear assembly 10 generates noise during the operation of the washing machine.